The studies proposed in this application are the outgrowth of previous and current studies of the bag cell neurosecretory organs of Aplysia californica. The long-term goal of the program of research has been, and remains, the development of a thoroughgoing characterization at the cellular and subcellular levels of the function of this neuroendocrine effector. Specific investigations are described in two major areas in this application: 1) Axonal transport and release of two polypeptide products from a single precursor species; and, 2) Location of target sites for the hormonally active polypeptide, and biochemical characterization of ligand-receptor interactions of these target sites. The former studies will employ subcellular fractionation, electron microscopy and counter-current dialysis for analysis of interactions between the product polypeptides and determination of their fates upon depolarization-induced secretion. The latter studies will, in addition, require use of autoradiographic, radioimmunoassay, and electrophysiologic procedures for locating and assessing the response of neural and non-neural target cells. It is anticipated that the results of these studies will yield important insights into the fundamental processes of neurosecretion and the behavioral consequences of hormone action.